Gyratory crushers are used for crushing ore, mineral and rock material to smaller sizes. Typically, the crusher comprises a crushing head mounted upon an elongate main shaft. A first crushing shell (typically referred to as a mantle) is mounted on the crushing head and a second crushing shell (typically referred to as a concave) is mounted on a frame such that the first and second crushing shells define together a crushing chamber through which the material to be crushed is passed. A driving device positioned at a lower region of the main shaft is configured to rotate an eccentric assembly positioned about the shaft to cause the crushing head to perform a gyratory pendulum movement and crush the material introduced in the crushing chamber. Primary crushers, such as jaw crushers, are heavy-duty machines designed to process large material sizes of the order of one meter. Secondary and tertiary crushers are intended to process relatively smaller feed materials typically of a size less than 35 centimeters and cone crushers represent a sub-category of gyratory crushers that are typically utilised as downstream crushers due to their high reduction ratios and low wear rates.
A variety of different mechanisms have been described to both axially and rotatably secure the outer crushing shell within the topshell so as to prevent the concave from being pushed out of the topshell and rotating with the gyroscopic precession of the mantle (mounted about the central shaft). U.S. Pat. No. 5,769,340 describes a positioning device in which the concave is provided with a plurality of tabs that sit radially between the concave and the topshell to provide respective abutment surfaces to frictionally grip radially outer regions of the concave so as to maintain it in position.
U.S. Pat. No. 5,915,638 describes the mounting of an outer crushing shell to the topshell via stop blocks that are received within key slots (formed at an upper annular rim of the topshell) to cooperate with separate and independently mounted wedge shaped keying elements that frictionally engage the topshell to provide a rotational lock.
WO 2004/110626 discloses a number of different embodiments for mounting a concave at a topshell via an intermediate spacer ring. The spacer ring is secured to the topshell via flanges that project radially outward from an upper annular rim of the ring to be seated within stepped regions formed in the upper annular rim of the topshell.
However, conventional arrangements are disadvantageous for a number of reasons. In particular, the upper and/or lower annular rims of the topshell are typically subjected to significant loading forces as the topshell is mated against additional components within the crusher such as a spider and the bottom shell. Removing excessive material from the respective topshell upper and lower rims to accommodate locking attachments that engage the crushing shell can weaken the topshell and increases the likelihood of stress concentrations and fracture propagation. Additionally, conventional locking mechanisms commonly employ an axially extending locking bolt that is secured into the topshell to provide the ‘stop’ for rotationally locking the crushing shell. It is not uncommon for such bolts to shear during use resulting in the concave rotating within the topshell and in some instances falling into the bottom shell and damaging further components of the crusher. Accordingly, what is required is a locking mechanism for a crushing shell that addresses the above problems.